Apparatus

ABSTRACT

[Object] To enable a CP with a more appropriate length in MBSFN subframes to be used. 
     [Solution] There is provided an apparatus including an acquisition unit configured to acquire a result of measurement of delay between identical signals transmitted in an MBSFN area, and a decision unit configured to decide a cyclic prefix length for an MBSFN subframe of the MBSFN area based on the result of the measurement.

TECHNICAL FIELD

The present disclosure relates to an apparatus.

BACKGROUND ART

In cellular networks, multicast broadcast multimedia services (MBMS) hasbeen put to practical use as a scheme of delivering the same content asbroadcast content to a plurality of users. In particular, in Long TermEvolution (LTE), an MBMS over single frequency network (MBSFN) in whichbase stations of a plurality of cells are mutually synchronized todeliver the same content has been standardized. Through an MBSFN,received signals from a plurality of base stations are combined so thatreception quality can be improved.

Technologies have been proposed.

In an MBSFN, a plurality of base stations transmit the same data withthe same radio resources. Therefore, in order to allow a long delayspread, an extended cyclic prefix (CP) of 16.7 us or 33.3 us is used inMBSFN regions of MBSFN subframes. When the extended CP of 16.7 us isused, 6 OFDM symbols are included in one slot. That is, 12 OFDM symbolsare included in one subframe. On the other hand, when the extended CP of33.3 us is used, 3 OFDM symbols are included in one slot. That is, 6OFDM symbols are included in one subframe.

For example, Non-Patent Literature 1 discloses a technology standardizedfor MBMS and MBSFN.

CITATION LIST Non-Patent Literature

Non-Patent Literature 1: 3GPP TS 36.331 V11. 5.0 (2013-09) LTE; EvolvedUniversal Terrestrial Radio Access (E-UTRA); Radio Resource Control(RRC); Protocol Specification

SUMMARY OF INVENTION Technical Problem

However, when an MBSFN area is formed by a plurality of small cells, adelay spread of the MBSFN area can be small since the size of the MBSFNarea is small. For this reason, for example, when an extended CP isused, the length of the CP is larger than necessary, and overhead mayconsequently be increased.

Accordingly, it is desirable to provide a structure enabling a CP with amore appropriate length in MBSFN subframes to be used.

Advantageous Effects of Invention

According to the present disclosure, there is provided an apparatusincluding: an acquisition unit configured to acquire a result ofmeasurement of delay between identical signals transmitted in an MBSFNarea; and a decision unit configured to decide a cyclic prefix lengthfor an MBSFN subframe of the MBSFN area based on the result of themeasurement.

According to the present disclosure, there is provided an apparatusincluding: an acquisition unit configured to acquire a result ofmeasurement of delay between identical signals transmitted in an MBSFNarea; and a supply unit configured to supply the result of themeasurement to a control apparatus that decides a cyclic prefix lengthfor an MBSFN subframe of the MBSFN area.

According to the present disclosure, there is provided an apparatusincluding: a measurement unit configured to measure delay betweenidentical signals transmitted in an MBSFN area.

According to the present disclosure, there is provided an apparatusincluding: a control unit configured to control transmission such thatonly an MBSFN reference signal is transmitted in at least one symbol inan MBSFN region of a specific MBSFN subframe.

According to the present disclosure, there is provided an apparatusincluding: an acquisition unit configured to acquire specificationinformation for specifying a cyclic prefix length for an MBSFN subframeof an MBSFN area; and a control unit configured to control transmissionof the specification information in a cell.

According to the present disclosure described above, it is possible touse the CP with a more appropriate length in the MBSFN subframes. Notethat the effects described above are not necessarily limited, and alongwith or instead of the effects, any effect that is desired to beintroduced in the present specification or other effects that can beexpected from the present specification may be exhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram illustrating an example of an MBSFNarea.

FIG. 2 is an explanatory diagram illustrating channels for an MBMS.

FIG. 3 is an explanatory diagram illustrating examples of MBSFNsubframes.

FIG. 4 is an explanatory diagram illustrating a first example ofresources and signals of the MBSFN subframes.

FIG. 5 is an explanatory diagram illustrating a second example ofresources and signals of the MBSFN subframes.

FIG. 6 is an explanatory diagram illustrating a first example ofresources and signals of normal subframes.

FIG. 7 is an explanatory diagram illustrating a second example ofresources and signals of the normal subframes.

FIG. 8 is an explanatory diagram illustrating an example of a cyclicprefix (CP).

FIG. 9 is an explanatory diagram illustrating examples of a cyclicprefix (CP) and an FFT processing window.

FIG. 10 is an explanatory diagram illustrating examples of subframes inwhich an MCCH is disposed.

FIG. 11 is an explanatory diagram illustrating examples of MBSFNsubframes.

FIG. 12 is an explanatory diagram illustrating examples of a PMCH and anMTCH mapped to the PMCH.

FIG. 13 is an explanatory diagram illustrating an example of a timing ofnotification of a change in information regarding the MCCH.

FIG. 14 is an explanatory diagram illustrating an example of theconfiguration of an LTE network supporting the MBSFN.

FIG. 15 is an explanatory diagram illustrating an example of an MBMScounting procedure.

FIG. 16 is an explanatory diagram illustrating an example of a schematicconfiguration of a communication system according to an embodiment ofthe present disclosure.

FIG. 17 is a block diagram illustrating an example of the configurationof a control apparatus according to a first embodiment.

FIG. 18 is an explanatory diagram illustrating an example of a result ofmeasurement of delay.

FIG. 19 is an explanatory diagram illustrating an example of MBMSsubframes.

FIG. 20 is a block diagram illustrating an example of the configurationof a small base station according to the first embodiment.

FIG. 21 is a block diagram illustrating an example of the configurationof the terminal apparatus according to the first embodiment.

FIG. 22 is an explanatory diagram illustrating an example of a specificscheme of measuring a delay spread.

FIG. 23 is a sequence diagram illustrating an example of a schematicflow of a process according to the first embodiment.

FIG. 24 is a block diagram illustrating an example of the configurationof a small base station according to a second embodiment.

FIG. 25 is a sequence diagram illustrating an example of a schematicflow of a process according to the second embodiment.

FIG. 26 is a block diagram illustrating an example of a schematicconfiguration of a server.

FIG. 27 is a block diagram illustrating a first example of a schematicconfiguration of an eNB.

FIG. 28 is a block diagram illustrating a second example of a schematicconfiguration of an eNB.

FIG. 29 is a block diagram illustrating an example of a schematicconfiguration of a smartphone.

FIG. 30 is a block diagram illustrating an example of a schematicconfiguration of a car navigation apparatus.

DESCRIPTION OF EMBODIMENT(S)

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the appended drawings. In thisspecification and the drawings, elements that have substantially thesame function and structure are denoted with the same reference signs,and repeated explanation is omitted.

The description will be made in the following order.

1. Introduction

2. Schematic configuration of communication system

3. First Embodiment

-   -   3.1. Configuration of control apparatus    -   3.2. Configuration of small base station    -   3.3. Configuration of terminal apparatus    -   3.4. Flow of process

4. Second Embodiment

-   -   4.1. Configuration of control apparatus    -   4.2. Configuration of small base station    -   4.3. Flow of process

5. Application examples

-   -   5.1. Application example of control apparatus    -   5.2. Application example of small base station    -   5.3. Application example of terminal apparatus

6. Conclusion

1. INTRODUCTION

First, technologies for MBMS and an MBSFN will be described withreference to FIGS. 1 to 15.

(MBSFN Area)

In an MBSFN, a plurality of base stations are mutually synchronized todeliver the same content. That is, in an MBSFN, a plurality of basestations transmit the same data with the same radio resources. Cells(that is, a plurality of cells) of the plurality of base stations arereferred to as MBSFN areas. Each cell can belong to a maximum of 8 MBSFNareas. Hereinafter, a specific example of an MBSFN area will bedescribed with reference to FIG. 1.

FIG. 1 is an explanatory diagram illustrating an example of an MBSFNarea. Referring to FIG. 1, cells #1 to #15 are illustrated. In thisexample, an MBSFN area 0 includes cells #1 to #3 and #5 to #8, an MBSFNarea 1 includes cells #7, #9, #10, and #13, and an MBSFN area 255includes cells #8, #9, and #11 to #15. Cell #7 belongs to both of theMBSFN area 0 and the MBSFN area 1. Cell #8 belongs to both of the MBSFNarea 0 and the MBSFN area 255. Cell #9 belongs to both of the MBSFN area1 and the MBSFN area 255. Cell #4 belongs to neither the MBSFN area 1nor the MBSFN area.

(Channels Related to MBMS)

Logical channels, transport channels, and physical channels are decidedfor the MBMS. Hereinafter, this point will be described with referenceto FIG. 2. FIG. 2 is an explanatory diagram illustrating channels for anMBMS. Referring to FIG. 2, logical channels, transport channels, andphysical channels decided in LTE are illustrated. In particular, amulticast control channel (MCCH) and a multicast traffic channel (MTCH)are decided as the logical channels for the MBMS. The MCCH is a channelfor transmitting control information such as an MBSFN area configurationmessage and an MBM counting request messega (MBMS). The MTCH is achannel for transmitting data of the MBMS. A physical multicast channel(PMCH) is decided as the physical channel for the MBMS. Both of thecontrol information mapped to the MCCH and data mapped to the MTCH aremapped to the PMCH via a multicast channel (MCH) which is a transportchannel.

(MBSFN Subframes)

The MBSFN is transmitted with MBSFN subframes. The MBSFN subframe isindicated by a radio frame allocation period, a radio frame allocationoffset, and a subframe allocation. Hereinafter, specific examples of theMBSFN subframes will be described with reference to FIG. 3.

FIG. 3 is an explanatory diagram illustrating examples of the MBSFNsubframes. Referring to FIG. 3, subframes included in a radio frame ofeach system frame number (SFN) are illustrated. In this example, theradio frame allocation period is 8 and the radio frame allocation offsetis 2. The subframe allocation is a 4 frame pattern (24 bits). Therefore,a radio frame of the SFN satisfying “SFN mod 8=2” (that is, the SFN of2, 10, 18, or the like) and 3 radio frames continuously subsequent tothe radio frame are radio frames for the MBSFN. In this example,frequency division duplexing (FDD) is adopted and the subframeallocation is “011010 011010 011010 011010.” When the FDD is adopted,bits of the subframe allocation indicate subframes #1, #2, #3, #6, #7,and #8. Therefore, of the radio frames, subframes #2, #3, and #7 areMBSFN subframes.

Subframes with which system information and paging information aretransmitted are not used as the MBSFN subframes. Thus, when the FDD isadopted, subframes #0, #4, #5, and #9 are not used as the MBSFNsubframes. When time division duplexing (TDD) is adopted, subframes #0,#1, #2, #5, and #6 are not used as the MBSFN subframes.

For example, a terminal apparatus is notified of the MBSFN subframeswith system information block (SIB) 2. Accordingly, the terminalapparatus can know an MBSFN area. The terminal apparatus is notified ofthe MBSFN subframes of each MBSFN area also with control informationmapped to the MCCH (MBSFN area configuration message), as will bedescribed below.

(Resources and Signals of MBSFN Subframes)

Number of OFDM Symbols

In the MBSFN, the plurality of base stations transmit the same data withthe same radio resources. Therefore, in order to permit a long delayspread, an extended CP of 16.7 us or 33.3 us is used in MBSFN regions ofthe MBSFN subframes. When the extended CP of 16.7 us is used, 6 OFDMsymbols are included in one slot. That is, 12 OFDM symbols are includedin one subframe. On the other hand when the extended CP of 33.3 us isused, 3 OFDM symbols are included in one slot. That is, 6 OFDM symbolsare included in one subframe.

Reference Signal (RS)

The base stations of the cells belonging to an MBSFN area transmit thesame signal particularly in the MBSFN regions of the MBSFN subframes.Therefore, such a base station does not transmit a cell-specificreference signal (CRS) in the MBSFN region. Instead, such a base stationtransmits an MBSFN reference signal (MBSFN-RS) which is a referencesignal for the MBSFN. The MBSFN-RS is transmitted with the same radioresources (that is, the same resource elements) in all the cellsbelonging to an MBSFN area.

Specific Example

FIG. 4 is an explanatory diagram illustrating first examples ofresources and signals of the MBSFN subframes. Referring to FIG. 4, tworesource blocks (RB) arranged in a time direction in the MBSFN subframesare illustrated. In this example, the extended CP of 16.7 us is used,and the MBSFN subframes include 12 OFDM symbols in the time direction.The MBSFN subframe includes a non-MBSFN region extending over the firsttwo OFDM symbols among the 12 OFDM symbols and an MBSFN regioncontinuing after the non-MBSFN region. In the non-MBSFN region, the CRScan be transmitted. On the other hand, in the MBSFN region, a commonMBSFN-RS between cells belonging to the MBSFN area is transmitted. Inthe MBSFN region, the control information mapped to the MCCH and/or thedata mapped to the MTCH are transmitted.

FIG. 5 is an explanatory diagram illustrating second examples ofresources and signals of the MBSFN subframes. Referring to FIG. 5, tworesource blocks (RB) arranged in a time direction in the MBSFN subframesare illustrated. In this example, the extended CP of 33.3 us is used,and the MBSFN subframes include 6 OFDM symbols in the time direction.The MBSFN subframe includes a non-MBSFN region extending over the firstone OFDM symbol among the 6 OFDM symbols and an MBSFN region continuingafter the non-MBSFN region. In the non-MBSFN region, the CRS can betransmitted (not illustrated). On the other hand, in the MBSFN region, acommon MBSFN-RS between cells belonging to the MBSFN area istransmitted. In the MBSFN region, the control information mapped to theMCCH and/or the data mapped to the MTCH are transmitted.

(Resources and Signals of Normal Subframes)

Number of OFDM Symbols

In the normal subframes which are not the MBSFN subframes, a normal CPor the extended CP of 16.7 us is used. The length of the normal CP is5.1 us in the first OFDM symbol in the slot and is 4.7 us in the otherOFDM symbols. When the normal CP is used, 7 OFDM symbols are included inone slot. That is, 14 OFDM symbols are included in one subframe. On theother hand, when the extended CP of 16.7 us is used, 6 OFDM symbols areincluded in one slot. That is, 12 OFDM symbols are included in onesubframe.

Reference Signal (RS)

The base station transmits the CRS in the normal subframes. The CRS isused, for example, to select a cell, estimate a channel, and detectsynchronization of downlink data.

Specific Example

FIG. 6 is an explanatory diagram illustrating a first example ofresources and signals of the normal subframes. Referring to FIG. 6, tworesource blocks (RBs) arranged in the time direction in the normalsubframes are illustrated. In this example, the normal CP is used andthe subframes include 14 OFDM symbols in the time direction. The CRS istransmitted with a predetermined resource element (RE) in each RB. Thepredetermined RE is set for each cell.

FIG. 7 is an explanatory diagram illustrating a second example ofresources and signals of the normal subframes. Referring to FIG. 7, tworesource blocks (RB) arranged in the time direction in the normalsubframes are illustrated. In this example, the extended CP of 16.7 usis used and the subframes include 12 OFDM symbols in the time direction.Even in this case, the CRS is transmitted with a predetermined resourceelement (RE) in each RB. The predetermined RE is set for each cell.

(Cyclic Prefix (CP))

The OFDM symbol includes a cyclic prefix (CP) and a main body. The CP isgenerated by copying a part of a waveform of the main body. Hereinafter,a specific example of this point will be described with reference toFIG. 8.

FIG. 8 is an explanatory diagram illustrating an example of the cyclicprefix (CP). Referring to FIG. 8, the waveform of the OFDM symbol isillustrated. The OFDM symbol includes the CP and the main body. The CPis generated by copying a final portion of the main body and is prefixedbefore the main body.

When a delay spread by a multipath falls in the length of the CP, asignal is fully expressed in a fast Fourier transform (FFT) processingwindow and is accurately combined by FFT processing. Conversely, when adelay spread by a multipath does not fall in the length of the CP, asignal is not fully expressed in the FFT processing window andinter-symbol interference may occur. As a result, reception performancemay deteriorate. Hereinafter, a specific example of this point will bedescribed with reference to FIG. 9.

FIG. 9 is an explanatory diagram illustrating examples of the cyclicprefix (CP) and the FFT processing window. Referring to FIG. 9, a firstdelay spread component and a second delay spread component areillustrated. The second delay spread component is received later thanthe first delay spread component by a receiver. A difference in areception timing between the first delay spread component and the seconddelay spread component is a delay spread. When the delay spread isshorter than the length of the CP, a signal is fully expressed in theFFT processing window and is accurately combined.

The terminal apparatus can also determine the length of the CP which isbeing used. As one example, the terminal apparatus can determine thelength of the CP in which a synchronization signal, a reference signal,master report information, or the like is subjected to optimumdemodulation among a plurality of lengths of the CPs as the length ofthe CP which is being used. As another example, the terminal apparatuscan determine the length of the CP which is being used through waveformanalysis of the synchronization signal or the reference signal. As yetanother example, the terminal apparatus can determine the number ofsymbols in the subframes and determine the length of the CP from thenumber of symbols. As still another example, the terminal apparatus candetermine the length of the CP from disposition of the reference signalsin the subframes.

(MCCH, MTCH, and PMCH)

Relation Between MBSFN Area and MCCH

One MCCH corresponds to one MBSFN area. That is, the MCCH is present ineach MBSFN area to which the cell belongs.

SIB 13

An SIB 13 indicates a subframe or the like in which the MCCH is disposedand the terminal apparatus is notified of the SIB 13. More specifically,the SIB 13 includes an MCCH repetition period, an MCCH offset, andsubframe allocation information. Hereinafter, specific examples of thesubframes in which the MCCH is disposed will be described with referenceto FIG. 10.

FIG. 10 is an explanatory diagram illustrating examples of the subframesin which an MCCH is disposed. Referring to FIG. 10, the subframesincluded in a radio frame of each system frame number (SFN) areillustrated. The MBSFN subframes of this example are the same as theMBSFN subframes illustrated in FIG. 3. In this example, the MCCHrepetition period is 32 and the MCCH offset is 5. Therefore, a radioframe of the SFN satisfying “SFN mod 32=5” (that is, the SFN of 5, 37,or the like) is a radio frame in which the MCCH is disposed. In thisexample, the subframe allocation information is “010000.” When the FDDis adopted, bits of the subframe allocation indicate subframes #1, #2,#3, #6, #7, and #8. Therefore, of the radio frames, subframe #2 is asubframe in which the MCCH is disposed. In this way, the MCCH isperiodically disposed in the MBSFN subframe.

The MCCH and the MTCH are multiplexed in a media access control (MAC)layer, but the terminal apparatus can demodulate the MCCH and the MTCHby multiplexing information of an MAC header.

MBSFN Area Configuration Message

The MBSFN area configuration message is mapped to the MCCH.

Common Subframe Allocation (CSA)

First, the MBSFN area configuration message includes a common subframeallocation (CSA) pattern list and a CSA period. The informationindicates the MBSFN subframes of the MBSFN area. The CSA pattern listincludes a radio frame allocation period, a radio frame allocationoffset, and a subframe allocation. Hereinafter, specific examples of theMBSFN subframes indicated by the information will be described withreference to FIG. 11.

FIG. 11 is an explanatory diagram illustrating examples of the MBSFNsubframes. Referring to FIG. 11, radio frames extending over the CSAperiod are illustrated. In this example, the CSA period is 32 radioframes. In this example, the CSA pattern list includes entries 1 and 2.In the entry 1, the radio frame allocation period is 16, the radio frameallocation offset is 0, and the subframe allocation is “100100” of 1frame pattern (6 bits). Thus, the MBSFN subframes of the entry 1 aresubframes #1 and #6 in 2 radio frames in which the SFN is 0 and 16. Inthe entry 2, the radio frame allocation period is 4, the radio frameallocation offset is 3, and the subframe allocation is “001001” of 1frame pattern (6 bits). Thus, the MBSFN subframes of the entry 2 aresubframes #3 and #8 in 8 radio frames in which the SFN is 3, 7, 11, 15,19, 23, 27, and 31. Thus, in this example, a total of 20 subframes inthe CSA period are illustrated as the MBSFN subframes.

PMCH Information

Further, the MBSFN area configuration message includes a PMCHinformation list. The PMCH information list indicates the MBSFNsubframes in which each PMCH is disposed and one or more MTCHs mapped toeach PMCH. In the first subframe in the PMCH, MCH scheduling information(MSI) which is scheduling information of the MTCH mapped to the PMCH istransmitted. The PMCH information list also indicates a transmissionperiod of the MSI. The period is referred to as an MCH scheduling period(MSP). Hereinafter, examples of the PMCH and the MTCH mapped to the PMCHwill be described with reference to FIG. 12.

FIG. 12 is an explanatory diagram illustrating examples of the PMCH andan MTCH mapped to the PMCH. Referring to FIG. 12, four sets of 20 MBSFNsubframes described with reference to FIG. 11 are illustrated. That is,80 MBSFN subframes over four CSA periods (that is, CSA periods 1 to 4)are illustrated. In this example, of the 20 MBSFN subframes in the CSAperiods (32 radio frames), the first to seventh subframes are allocatedto a PMCH 1. The eighth to eleventh subframes are allocated to a PMCH 2,the twelfth to fifteenth subframes are allocated to a PMCH 3, and thesixteenth to twentieth subframes are allocated to a PMCH 4. Logicalchannels 1 and 2 (that is, MTCHs 1 and 2) are mapped to the PMCH 1. Alogical channel 3 (that is, an MTCH 3) is mapped to the PMCH 2, alogical channel 4 (that is, an MTCH 4) is mapped to the PMCH 3, and alogical channel 5 (that is, an MTCH 5) is mapped to the PMCH 4. Whenattention is paid to the PMCH 1, the MSP of the PMCH 1 is 64 radioframes and the MSI is transmitted with the PMCH 1 every two CSA periods.During the CSA periods 1 and 2, the logical channel 1 (that is, the MTCH1) is disposed in the first to ninth subframes among the MBSFN subframesallocated to the PMCH 1. The logical channel 2 (that is, the MTCH 2) isdisposed in the tenth to the thirteenth subframes. No logical channel(MTCH) is disposed in the fourteenth subframe. During the CSA periods 3and 4, the logical channel 1 is disposed in the first to eighthsubframes among the MBSFN subframes allocated to the PMCH 1. The logicalchannel 2 is disposed in the ninth to the twelfth subframes. No logicalchannel (MTCH) is disposed in the thirteenth and fourteenth subframe. Asillustrated in FIG. 12, the MCCH is also disposed in the MBSFN subframe.

(Notification of Change in MCCH)

When information regarding the MCCH is changed, all of the terminalapparatuses are notified of the change in the information regarding theMCCH with downlink control information (DCI) to be transmitted over aphysical downlink control channel (PDCCH) in the non-MBSFN region of theMBSFN subframe. Specifically, the DCI includes an MCCH changenotification indicator. The MCCH change notification indicator is an8-bit bitmap corresponding to each MBSFN area. In this notification,radio network temporary identity (MBMS RNTI), that is, M-RNTI, is used.

First, the change in the MCCH is notified of for an MCCH modificationperiod and the changed information is notified of for a subsequent MCCHmodification period. Hereinafter, a specific example of this point willbe described with reference to FIG. 13.

FIG. 13 is an explanatory diagram illustrating an example of a timing ofnotification of a change in information regarding the MCCH. Referring toFIG. 13, a first MCCH modification period (n) and a first MCCHmodification period (n+1) continuing from the first MCCH modificationperiod (n) are illustrated. In this way, the change in the informationregarding the MCCH is notified of for the first MCCH modification period(n), and subsequently the changed information is notified of for thesecond MCCH modification period (n+1). To ensure mobility of theterminal apparatus, the changed information is transmitted not only inthe first MCCH but also in subsequent MCCHs. The information regardingthe MCCH is changed over a relatively long time.

(System Configuration of MBSFN)

An example of the configuration of an LTE network supporting the MBSFNwill be described with reference to FIG. 14. FIG. 14 is an explanatorydiagram illustrating an example of the configuration of an LTE networksupporting the MBSFN. Referring to FIG. 14, the LTE network includes amulti-cell/multicast coordinate entity (MCE), a broadcast/multicastservice center (BM-SC), an MBMS gateway (GW), and a mobility managemententity (MME). Such nodes are logical nodes. The MCE causes an evolvedNode B (eNB) of a cell belonging to the MBSNF area to transmit the samedata with the same radio resources. Specifically, for example, the MCEperforms scheduling related to the MBSNF in the MBSNF area. The BM-SCperforms data flow control in a core network, authentication, charging,and the like of a contents provider. The MBMS-GW performs transmissionof multicast IP packets from the BM-SC to the eNB and a process on asession control signal via the MME. The MME performs a process on anon-access stratum (NAS).

The example in which one MCE corresponds to a plurality of eNBs has beendescribed, but the MCE is not limited to the related example. Forexample, each eNB may include the MCE.

(Counting Procedure)

In the MBSFN, information regarding interest in an MBMS service iscollected through an MBMS counting procedure. Hereinafter, the MBMScounting procedure will be described with reference to FIG. 15.

FIG. 15 is an explanatory diagram illustrating an example of an MBMScounting procedure. Referring to FIG. 15, first, when the informationregarding the MCCH is changed and the terminal apparatus enters theMBSFN area, the terminal apparatus receives an MBMS counting requestmessage along with the MBSFN area configuration message. When theterminal apparatus is in an RRC connection mode and an MBMS service inwhich the terminal apparatus is interested is included in a list of anMBMS counting request, the terminal apparatus transmits an MBMS countingresponse message including an identifier of the MBMS service to anetwork. Accordingly, for each MBMS service, the number of terminalapparatuses which receive the MBMS service or are interested in the MBMSservice can be counted. Therefore, starting and ending of the MBMSservice can be controlled according to a counting result.

(Operation of Terminal)

The terminal apparatus receives the SIB 13 and specifies subframes inwhich the MCCH is disposed. Then, the terminal apparatus receives theMBSFN area configuration message as the information regarding the MCCHwith the subframes and specifies the PMCH to which the MTCH of a desiredMBMS session is mapped. Thereafter, the terminal apparatus receives theMSI of the PMCH to which the MTCH is mapped and specifies the subframesin which the MTCH is disposed. Then, the terminal apparatus receivesdata of the MTCH (that is, data of the desired MBMS session) with thesubframes. According to such an operation, the terminal apparatus canreceive the data with only necessary minimum subframes and can sleepwith other subframes. Therefore, power consumption of the terminalapparatus is suppressed.

2. SCHEMATIC CONFIGURATION OF COMMUNICATION SYSTEM

Next, a schematic configuration of a communication system 1 according toan embodiment of the present disclosure will be described with referenceto FIG. 16. FIG. 16 is an explanatory diagram illustrating an example ofa schematic configuration of the communication system 1 according to thepresent disclosure. Referring to FIG. 13, the communication system 1includes a macro base station 11, a control apparatus 100, small basestations 200, and terminal apparatuses 400. The communication system 1is, for example, a system that conforms to LTE, LTE-Advanced, or acommunication standard equivalent thereto.

The macro base station 11 performs radio communication with a terminalapparatus located in a macro cell 10. The macro base station 11 isconnected to a core network 40.

The small base station 200 performs radio communication with a terminalapparatus located in a small cell 20. For example, the small cell 20partially or entirely overlaps the macro cell 10. The plurality of smallcells 20 belong to an identical MBSNF area 30. In the MBSNF area 30, theplurality of small base stations 200 transmits the same signal with thesame radio resources in the MBSNF subframes. For example, the smallcells 20 are femtocells and the small base stations 200 are connected tothe Internet 50.

The control apparatus 100 operates as an MCE in the plurality of smallbase stations 200. For example, the control apparatus 100 also operatesas an MBMS-GW. For example, the control apparatus 100 is connected tothe Internet 50 and communicates with the small base stations 200 viathe Internet 50. The control apparatus 100 can communicate with a corenetwork node (for example, an MME) located in the core network 40 and/orthe macro base station 11 via the Internet 50.

The terminal apparatus 400 performs radio communication with the basestation. For example, when the terminal apparatus 400 is located in themacro cell 10, the terminal apparatus 300 performs radio communicationwith the macro base station 11. When the terminal apparatus 300 islocated in the small cell 20, the terminal apparatus 300 performs radiocommunication with the small base station 200.

The schematic configuration of the communication system 1 according tothe embodiment of the present disclosure has been described above.According to the embodiment of the present disclosure, the controlapparatus 100 acquires a result of measurement of delay betweenidentical signals transmitted in the MBSFN area 30. Based on the resultof the measurement, the control apparatus 100 decides the length of theCP for the MBSFN subframes of the MBSFN area 30. Accordingly, forexample, it is possible to use the CP with the more appropriate lengthin the MBSFN subframes.

3. FIRST EMBODIMENT

Next, a first embodiment of the present disclosure will be describedwith reference to FIGS. 17 to 23. According to the first embodiment, acontrol apparatus 100-1 acquires a result of measurement of delaybetween identical signals transmitted in the MBSFN area 30. Then, basedon the result of measurement, the control apparatus 100-1 decides thelength of the CP for the MBSFN subframes of the MBSFN area 30. Inparticular, according to the first embodiment, the measurement of thedelay is performed by a terminal apparatus 400-1.

<3.1. Configuration of Control Apparatus>

First, the configuration of a control apparatus 100-1 according to thefirst embodiment will be described with reference to FIGS. 17 to 19.FIG. 17 is a block diagram illustrating an example of the configurationof the control apparatus 100-1 according to the first embodiment.Referring to FIG. 17, the control apparatus 100-1 includes acommunication unit 110, a storage unit 120, and a processing unit 150.

(Communication Unit 110)

The communication unit 110 communicates with another apparatus. Forexample, the communication unit 110 communicates with a small basestation 200-1. More specifically, for example, the communication unit110 communicates with the small base station 200-1 via the Internet 50.The communication unit 110 can communicates with a core network node(for example, an MME) located in the core network and/or the macro basestation 11 via the Internet 50.

(Storage Unit 120)

The storage unit 120 temporarily or permanently stores a program anddata for an operation of the control apparatus 100-1.

(Processing Unit 150)

The processing unit 150 supplies various functions of the controlapparatus 100-1. The processing unit 150 includes a request unit 151, aninformation acquisition unit 153, a decision unit 155, and a controlunit 157.

(Request Unit 151)

The request unit 151 requests a small base station 200-1 of a small cell20 belonging to the MBSFN area 30 to supply the result of themeasurement of the delay between the identical signals (hereinafterreferred to as a “delay measurement result”) transmitted in the MBSFNarea 30.

For example, the request unit 151 requests the small base station 200-1of one small cell 20 belonging to the MBSFN area 30 to supply the delaymeasurement result. The request unit 151 may request the small basestations 200-1 of two or more small cells 20 belonging to the MBSFN area30 to supply the delay measurement result.

(Information Acquisition Unit 153)

The information acquisition unit 153 acquires the result of themeasurement of the delay between the identical signals (that is, thedelay measurement result) transmitted in the MBSFN area 30. Theidentical signals are transmitted by the base stations 200-1 of theplurality of small cells 20 belonging to the MBSFN area 30.

For example, as described above, the request unit 151 requests the smallbase station 200-1 to supply the delay measurement result. Then, thesmall base station 200-1 supplies the delay measurement result to thecontrol apparatus 100-1. The delay measurement result is stored in thestorage unit 120. The information acquisition unit 153 acquires thedelay measurement result from the storage unit 120.

Measurement Entity

In the first embodiment, the delay measurement result is a result ofmeasurement by the terminal apparatus 400-1. That is, the terminalapparatus 400-1 measures the delay and supplies the result of themeasurement of the delay (that is, the delay measurement result) to thesmall base station 200-1. Then, for example, the small base station200-1 supplies the delay measurement result to the control apparatus100-1. Accordingly, for example, even when the small base station 200-1has no delay measurement function, the delay measurement result can beobtained.

Delay Measurement Result

For example, the delay measurement result is a delay spread between theidentical signals transmitted in the MBSFN area 30.

As a first example, the delay measurement result is a delay spreadbetween one signal (for example, a first received signal) and anothersignal among the identical signals transmitted in the MBSFN area 30.Hereinafter, a specific example of this point will be described withreference to FIG. 18.

FIG. 18 is an explanatory diagram illustrating an example of the delaymeasurement result. Referring to FIG. 18, four identical signalsreceived at different timings are illustrated. Referring to FIG. 18,first to fourth received signals are illustrated. For example, after thefirst signal is received first, the second, third, and fourth signalsare sequentially received. A delay spread between the first and secondsignals is D₂, a delay spread between the first and third signals is D₃,and a delay spread between the first and fourth signals is D₄. In thiscase, the delay measurement result is, for example, a set of delayspreads D₂, D₃, and D₄. Such a delay measurement result can also be saidto be information indicating a delay distribution.

As a second example, the delay measurement result is a delay spreadbetween the signal received first and the signal received last among theidentical signals transmitted in the MBSFN area 30. That is, the delaymeasurement result is a maximum delay spread. For example, referringback to FIG. 18, the delay measurement result is the delay spread D₄.

Of course, the delay measurement result may also be another delayspread. Of course, the delay spread may not be a measurement value, butmay be information corresponding to the measurement value (for example,an index corresponding to the measurement value among a plurality ofindexes indicating the delay spreads).

In accordance with such a delay measurement result (delay spread), forexample, an appropriate length of the CP for allowing the delay spreadcan be decided.

The delay measurement result is not limited to the delay spread, but maybe other information. For example, the delay measurement result may beother information indicating delay between identical signals. The delaymeasurement result may be information indicating the length of the CPallowing measured delay.

(Decision Unit 155)

Based on the delay measurement result, the decision unit 155 decides thelength of the CP for the MBSFN subframes of the MBSFN area 30.

Candidates for Length of CP

For example, the decision unit 155 decides one candidate for the lengthof the CP among a plurality of candidates for the length of the CP asthe length of the CP for the MBSFN subframes of the MBSFN area 30.

The plurality of candidates for the length of the CP include the lengthof a normal CP and the length of an extended CP. As one example, theplurality of candidates for the length of the CP are three lengths ofthe CP including the length of the normal CP (for example, 5.1 us withthe first symbol and 4.7 us with another symbol in a slot) and 16.7 usand 33.3 us which are lengths of the extended CP. Therefore, forexample, the decision unit 155 can decide the length of the normal CP asthe length of the CP for the MBSFN subframes of the MBSFN area 30.Accordingly, for example, when the delay spread in the MBSFN area 30 issmall, overhead can be decreased.

Decision Based on Delay Measurement Result

For example, based on the delay measurement result, the decision unit155 decides the length of the CP allowing maximum delay in the MBSFNarea 30 as the length of the CP for the MBSFN subframes of the MBSFNarea 30.

As described above, for example, the delay measurement result is thedelay spread between the identical signals transmitted in the MBSFN area30. In this case, for example, the decision unit 155 specifies themaximum delay spread from the delay measurement result and decides alonger candidate for the length of the CP than the maximum delay spreadamong the plurality of candidates for the length of the CP as the lengthof the CP for the MBSFN subframes of the MBSFN area 30. For example,when the maximum delay spread is shorter than the length of the normalCP, the decision unit 155 decides the length of the normal CP as thelength of the CP for the MBSFN subframes of the MBSFN area 30.

Decision of Number of Symbols of MBSFN Subframes

For example, when the length of the CP is decided, the number of symbolsincluded in the MBSFN subframes is also decided. Therefore, the decisionunit 155 can also be said to decide the number of symbols included inthe MBSFN subframes.

For example, the length of the normal CP is decided as the length of theCP for the MBSFN subframes of the MBSFN area 30. In this case, thenumber of symbols included in the MBSFN subframes is 14. That is, whenthe length of the CP for the MBSFN subframes is the length of the normalCP, the MBSFN subframes include 14 OFDM symbols. Hereinafter, a specificexample of this point will be described with reference to FIG. 19.

FIG. 19 is an explanatory diagram illustrating examples of the MBMSsubframes. Referring to FIG. 19, two resource blocks (RB) arranged inthe time direction in the MBSFN subframes are illustrated. In thisexample, the length of the CP is the length of the normal CP, and theMBSFN subframes include 14 OFDM symbols in the time direction. The MBSFNsubframes includes a non-MBSFN region extending over the first threeOFDM symbols among the 14 OFDM symbols and an MBSFN region continuingafter the non-MBSFN region. In the non-MBSFN region, the CRS can betransmitted. In the MBSFN region, an MBSFN-RS is transmitted.

For example, 16.7 us which is the length of the extended CP is decidedas the length of the CP for the MBSFN subframes of the MBSFN area 30. Inthis case, as illustrated in FIG. 4, the number of symbols included inthe MBSFN subframes is 12 and the length of the non-MBSFN region is 2.For example, 33.3 us which is the length of the extended CP is decidedas the length of the CP for the MBSFN subframes of the MBSFN area 30. Inthis case, as illustrated in FIG. 5, the number of symbols included inthe MBSFN subframes is 6 and a non-MBSFN region length is 1.

As described above, when the number of symbols included in the MBSFNsubframes is decided, the non-MBSFN region length of the MBSFN subframesis also decided. Therefore, the decision unit 155 can also be said todecide the non-MBSFN region length of the MBSFN subframes.

(Control Unit 157)

The control unit 157 causes the small base station 200-1 to perform theoperation of the MBSFN.

For example, the control unit 157 requests the small base station 200-1to start an MBMS session. More specifically, for example, the controlunit 157 transmits the MBMS session start request message to the smallbase station 200-1.

For example, the control unit 157 performs the MBMS scheduling andsupplies the MBMS scheduling information to the small base station200-1. More specifically, for example, the control unit 157 transmitsthe MBMS scheduling information message to the small base station 200-1.

As described above, the length of the CP for the MBSFN subframes of theMBSFN area 30 is decided. Then, the control unit 137 transmits the MBMSsession start request message or the MBMS scheduling information messageincluding the specifying information for specifying the length of the CP(for example, the length of the CP, the number of symbols, or thenon-MBSFN region length) to the small base station 200-1 of the smallcell 20 belonging to the MBSFN area 30. As a result, the small basestation 200-1 uses the decided length of the CP.

<3.2. Configuration of Small Base Station>

Next, the configuration of the small base station 200-1 according to thefirst embodiment will be described with reference to FIG. 20. FIG. 20 isa block diagram illustrating an example of the configuration of thesmall base station 200-1 according to the first embodiment. Referring toFIG. 20, the small base station 200-1 includes an antenna unit 210, aradio communication unit 220, a network communication unit 230, astorage unit 240, and a processing unit 270.

(Antenna Unit 210)

The antenna unit 210 radiates a signal output by the radio communicationunit 220 as radio waves to a space. The antenna unit 210 converts spaceradio waves into a signal and outputs the signal to the radiocommunication unit 220.

(Radio Communication Unit 220)

The radio communication unit 220 performs radio communication. Forexample, the radio communication unit 220 transmits a downlink signal tothe terminal apparatus 400-1. The radio communication unit 220 receivesan uplink signal from the terminal apparatus 400-1.

(Network Communication Unit 230)

The network communication unit 230 communicates with another node. Forexample, the network communication unit 230 communicates with a controlapparatus 100-1. For example, the network communication unit 230communicates with a core network node located in the core network 40and/or the macro base station 11. The network communication unit 230communicates with another node via the Internet 50.

(Storage Unit 240)

The storage unit 240 temporarily or permanently stores a program anddata for an operation of the small base station 200-1.

(Processing Unit 270)

The processing unit 270 supplies various functions of the small basestation 200-1. The processing unit 270 includes a request unit 271, afirst information acquisition unit 273, an information supply unit 275,a second information acquisition unit 277, and a transmission controlunit 279.

(Request Unit 271)

The request unit 271 requests the terminal apparatus 400-1 connected tothe small base station 200-1 to supply the result of the measurement ofthe delay between the identical signals (that is, the delay measurementresult) transmitted in the MBSFN area 30.

For example, when the small cell 20 of the small base station 200-1belongs to the MBSFN area 30, the control apparatus 100-1 requests thesmall base station 200-1 to supply the delay measurement result. Then,the request unit 271 requests the terminal apparatus 400-1 connected tothe small base station 200-1 to supply the delay measurement result.

For example, the request unit 271 requests one terminal apparatus 400-1connected to the small base station 200-1 to supply the delaymeasurement result. The request unit 271 may request two or moreterminal apparatuses 400-1 connected to the small base station 200-1 tosupply the delay measurement result.

As will be described below, for example, to measure the delay, only theMBSFN-RSs are transmitted in at least one symbol of the MBSFN region ofthe specific MBSFN subframes. Therefore, for example, the request unit271 notifies the terminal apparatus 400-1 of the specific MBSFNsubframes.

(First Information Acquisition Unit 273)

The first information acquisition unit 273 acquires the result of themeasurement of the delay (that is, the delay measurement result) betweenthe identical signals transmitted in the MBSFN area 30. The identicalsignals are transmitted by the base stations 200-1 of the plurality ofsmall cells 20 belonging to the MBSFN area 30.

For example, as described above, the request unit 271 requests theterminal apparatus 400-1 connected to the small base station 200-1 tosupply the delay measurement result. Then, the terminal apparatus 400-1supplies the delay measurement result to the small base station 200-1.The delay measurement result is stored in the storage unit 240. Thefirst information acquisition unit 273 acquires the delay measurementresult from the storage unit 240.

For example, the delay measurement result is a delay spread between theidentical signals transmitted in the MBSFN area 30. The specific exampleof the delay spread has been described above. The delay measurementresult is not limited to the delay spread, but may be other information.For example, the delay measurement result may be other informationindicating delay between identical signals. The delay measurement resultmay be information indicating the length of the CP allowing the measureddelay.

As described above, the request unit 271 may request two or moreterminal apparatuses 400-1 connected to the small base station 200-1 tosupply the delay measurement results, and the first informationacquisition unit 273 may acquire the delay measurement results by thetwo or more terminal apparatuses 400-1. In this case, as one example,the first information acquisition unit 273 may acquire the delaymeasurement result by each of the two or more terminal apparatuses400-1. As another example, the processing unit 270 may generate a wholedelay measurement result (for example, a maximum delay spread) from theindividual delay measurement results by the two or more terminalapparatuses 400-1, and the first information acquisition unit 273 mayacquire the whole delay measurement result.

(Information Supply Unit 275)

The information supply unit 275 supplies the delay measurement result tothe control apparatus 100-1. For example, the information supply unit275 supplies the result of the measurement to the control apparatus100-1 via the network communication unit 230.

(Second Information Acquisition Unit 277)

The second information acquisition unit 277 acquires specificationinformation for specifying the length of the CP for the MBSFN subframesof the MBSFN area 30.

For example, the control apparatus 100-1 supplies the specificationinformation to the small base station 200-1. As described above, forexample, the control apparatus 100-1 supplies the specificationinformation to the small base station 200-1 in the MBMS session startrequest message or the MBMS scheduling information message. Then, thespecification information is stored in the storage unit 240. The secondinformation acquisition unit 277 acquires the specification informationfrom the storage unit 240. For example, the second informationacquisition unit 277 acquires a system information block including thespecification information. The system information block is, for example,the SIB 13.

The specification information is, for example, the length of the CP forthe MBSFN subframes of the MBSFN area 30, the number of symbols of theMBSFN subframes, or the non-MBSFN region length of the MBSFN subframes.When the specification information is the non-MBSFN region length, thespecification information may be included as the non-MBSFN region lengthin the SIB 13.

(Transmission Control Unit 279)

Transmission of Specification Information

The transmission control unit 279 controls the transmission of thespecification information (that is, the information for specifying thelength of the CP for the MBSFN subframes of the MBSFN area 30) in thesmall cell 20.

For example, the transmission control unit 279 controls the transmissionof the system information block (for example, the SIB 13) including thespecification information. As a specific process, for example, thetransmission control unit 279 maps signals of the system informationblock to radio resources (for example, resource blocks) for the systeminformation block. As a result, the system information block istransmitted in the small cell 20.

Accordingly, for example, the decided length of the CP can actually beused in the terminal apparatus 400-1. A burden of the determination ofthe length of the CP by the terminal apparatus 400-1 may be relieved.

Transmission of Signal in MBSFN Region

In the first embodiment, for example, the transmission control unit 279controls the transmission such that only the MBSFN-RSs are transmittedin at least one symbol of the MBSFN region of the specific MBSFNsubframes.

As a specific process, for example, the transmission control unit 279inserts the MBSFN-RSs in at least one symbol of the MBSFN region of theMBSFN subframes and does not map other signals. As a result, only theMBSFN-RSs are transmitted in at least the one symbol.

Accordingly, for example, a time signal waveform in at least one symbolof the MBSFN region becomes a known waveform in the terminal apparatus400-1. Therefore, the terminal apparatus 400-1 can know receptiontimings of the MBSFN-RSs transmitted by the small base stations 200-1 ofthe plurality of small cells 20 belonging to the MBSFN area 30. Thus,the terminal apparatus 400-1 can measure delay between the MBSFN-RSs(that is, the identical signals) transmitted in the MBSFN area 30.

<3.3. Configuration of Terminal Apparatus>

Next, the configuration of a terminal apparatus 400-1 according to thefirst embodiment will be described with reference to FIGS. 21 and 22.FIG. 21 is a block diagram illustrating an example of the configurationof the terminal apparatus 400-1 according to the first embodiment.Referring to FIG. 21, the terminal apparatus 400-1 includes an antennaunit 410, a radio communication unit 420, a storage unit 430, and aprocessing unit 460.

(Antenna Unit 410)

The antenna unit 410 radiates a signal output by the radio communicationunit 420 as radio waves to a space. The antenna unit 410 converts spaceradio waves into a signal and outputs the signal to the radiocommunication unit 420.

(Radio Communication Unit 420)

The radio communication unit 420 performs radio communication. Forexample, the radio communication unit 420 receives a downlink signalfrom a base station. The radio communication unit 420 transmits anuplink signal to the base station. The base station includes the smallbase station 200-1 and the macro base station 11.

(Storage Unit 430)

The storage unit 430 temporarily or permanently stores a program anddata for an operation of the terminal apparatus 400-1.

(Processing Unit 460)

The processing unit 460 supplies various functions of the terminalapparatus 400-1. The processing unit 460 includes a measurement unit 461and an information supply unit 463.

(Measurement Unit 461)

The measurement unit 461 measures delay between the identical signalstransmitted in the MBSFN area 30.

For example, the identical signals are the MBSFN-RSs. As describedabove, for example, only the MBSFN-RSs are transmitted in at least onesymbol of the MBSFN region of the specific MBSFN subframes. Therefore,the measurement unit 461 measures the delay between the MBSFN-RSstransmitted in at least the one symbol.

For example, the result of the measurement (that is, the delaymeasurement result) is a delay spread between the identical signalstransmitted in the MBSFN area 30. That is, the delay measurement resultis, for example, the delay spread between the MBSFN-RS. The specificexample of the delay spread has been described above. Hereinafter, anexample of a specific scheme of measuring the delay spread will bedescribed with reference to FIG. 22.

FIG. 22 is an explanatory diagram illustrating an example of thespecific scheme of measuring the delay spread. Referring to FIG. 22, anexample of a configuration for measuring the delay spread isillustrated. For example, as described above, only the MBSFN-RSs aretransmitted in at least one symbol of the MBSFN region of the specificMBSFN subframes. Thus, through the mapping of the symbols of theMBSFN-RSs (predetermined signals according to the MBSFN area 30), a fastFourier transform (IFFT), and insertion of the CP, the time signalwaveform transmitted in at least the one symbol can be reproduced. Thereproduced time signal waveform is input as a pilot signal to acorrelator through delay adjustment. The time signal waveform receivedthrough a radio frequency (RF) unit and an A/D converter or the like isalso input to the correlator. Then, the delay spread between theMBSFN-RSs (that is, the identical signals) transmitted in the MBSFN area30 is measured through the correlator and an integrator.

The delay measurement result is not limited to the delay spread, but maybe other information. For example, the delay measurement result may beother information indicating delay between the identical signals. Thedelay measurement result may be information indicating the length of theCP allowing the measured delay.

(Information Supply Unit 463)

The information supply unit 463 supplies the result of the measurement(that is, the delay measurement result) to the small base station 200-1.For example, the information supply unit 463 supplies the delaymeasurement result to the small base station 200-1 via the radiocommunication unit 420.

<3.4. Flow of Process>

Next, an example of a process according to the first embodiment will bedescribed with reference to FIG. 23. FIG. 23 is a sequence diagramillustrating an example of a schematic flow of the process according tothe first embodiment.

The control apparatus 100-1 requests the small base station 200-1 of thesmall cell 20 belonging to the MBSFN area 30 to supply the result of themeasurement of the delay (that is, the delay measurement result) betweenthe identical signals (for example, the MBSFN-RSs) transmitted in theMBSFN area 30 (S601). The small base station 200-1 requests the terminalapparatus 400-1 connected to the small base station 200-1 to supply thedelay measurement result (S603). Then, the terminal apparatus 400-1measures the delay between the identical signals (for example, theMBSFN-RSs) transmitted in the MBSFN area 30 (S605). The terminalapparatus 400-1 supplies the result of the measurement (that is, thedelay measurement result) to the small base station 200-1 (S607).Thereafter, the small base station 200-1 supplies the delay measurementresult to the control apparatus 100-1 (S609). Based on the delaymeasurement result, the control apparatus 100-1 decides the length ofthe CP for the MBSFN subframes of the MBSFN area 30 (S611).

Thereafter, the control apparatus 100-1 transmits the MBMS session startrequest message and the MBMS scheduling information message to the smallbase station 200-1 (S613 and S615). The MBMS session start requestmessage or the MBMS scheduling information message includes thespecification information for specifying the decided length of the CP.Then, the small base station 200-1 reports the system information block(for example, the SIB 13) including the specification information(S617).

The first embodiment has been described above. According to the firstembodiment, the control apparatus 100-1 acquires the result of themeasurement of the delay between the identical signals transmitted inthe MBSFN area 30. Then, based on the result of the measurement, thecontrol apparatus 100-1 decides the length of the CP for the MBSFNsubframes of the MBSFN area 30. Accordingly, for example, it is possibleto use the CP with the more appropriate length in the MBSFN subframes.

According to the first embodiment, the delay is measured by the terminalapparatus 400-1. Accordingly, for example, even when the small basestation 200-1 has no delay measurement function, the delay measurementresult can be obtained.

4. SECOND EMBODIMENT

Next, a second embodiment of the present disclosure will be describedwith reference to FIGS. 24 and 25. According to the second embodiment, acontrol apparatus 100-2 acquires a result of measurement of delaybetween identical signals transmitted in the MBSFN area 30. Then, basedon the result of the measurement, the control apparatus 100-2 decidesthe length of the CP for the MBSFN subframes of the MBSFN area 30. Inthe second embodiment, this point is the same as in the firstembodiment. In particular, according to the second embodiment, the delayis measured by a small base station 200-2.

<4.1. Configuration of Control Apparatus>

The description of the control apparatus 100-2 according to the secondembodiment is the same as, for example, the description of the controlapparatus 100-1 according to the first embodiment excluding thefollowing point (a measurement entity) (excluding differences inreference numerals). Thus, the repeated description will be omittedhere.

(Information Acquisition Unit 153)

Measurement Entity

The control apparatus 100-1 (the information acquisition unit 153)according to the first embodiment acquires the result of the measurement(delay measurement result) by the terminal apparatus 400-1. On the otherhand, the control apparatus 100-2 (information acquisition unit 153)according to the second embodiment acquires the result of measurement(delay measurement result) by the small base station 200-2. That is, thesmall base station 200-2 measures the delay between the identicalsignals in the MBSFN area 30 and supplies the result of the measurementof the delay (that is, the delay measurement result) to the controlapparatus 100-1. Accordingly, for example, the delay measurement resultcan be obtained without imposing a burden on the terminal apparatus400-2.

<4.2. Configuration of Small Base Station>

Next, the configuration of a small base station 200-2 according to thesecond embodiment will be described with reference to FIG. 24. FIG. 24is a block diagram illustrating an example of the configuration of thesmall base station 200-2 according to the second embodiment. Referringto FIG. 24, the small base station 200-2 includes an antenna unit 210, aradio communication unit 225, a network communication unit 230, astorage unit 240, and a processing unit 280.

For example, the description of the antenna unit 210, the networkcommunication unit 230, and the storage unit 240 are no differentbetween the first and second embodiments (excluding differences inreference numerals). Thus, only the radio communication unit 225 and theprocessing unit 280 will be described here and the repeated descriptionwill be omitted.

(Radio Communication Unit 225)

The radio communication unit 225 performs radio communication. Forexample, the radio communication unit 225 transmits a downlink signal tothe terminal apparatus 400-2. The radio communication unit 225 receivesan uplink signal from the terminal apparatus 400-2.

Further, in particular, in the second embodiment, the radiocommunication unit 225 receives a downlink signal from another smallbase station 200-2. The downlink signal includes a reference signal.

(Processing Unit 280)

The processing unit 280 supplies various functions of the small basestation 200-2. The processing unit 280 includes a measurement unit 281,a first information acquisition unit 283, an information supply unit285, a second information acquisition unit 287, and a transmissioncontrol unit 289.

The description of the information supply unit 285 and the secondinformation acquisition unit 287 according to the second embodiment arethe same as the description of the information supply unit 275 and thesecond information acquisition unit 277 according to the firstembodiment. Thus, here, only the measurement unit 281, the firstinformation acquisition unit 283, and the transmission control unit 289will be described and the repeated description will be omitted.

(Measurement Unit 281)

The measurement unit 281 measures delay between the identical signalstransmitted in the MBSFN area 30. The identical signals are transmittedto the base stations 200-1 of the plurality of small cells 20 belongingto the MBSFN area 30. For example, the identical signals are signalstransmitted in the MBSFN region of the MBSFN subframes (that is, theMBSFN-RSs and signals of the PMCHs). The measurement unit 281 measuresthe delay between the signals transmitted in the MBSFN region. Since thesmall cell 20 of the small base station 200-2 belongs to the MBSFN area30, the signals transmitted in the MBSFN region of the MBSFN subframesare supplied in advance to the small base station 200-2. Therefore, thesignals transmitted in the MBSFN region can be said to be known in thesmall base station 200-2.

For example, the result of the measurement (that is, the delaymeasurement result) is a delay spread between the identical signalstransmitted in the MBSFN area 30. That is, the delay measurement resultis, for example, a delay spread between the signals transmitted in theMBSFN region. The specific example of the delay spread has beendescribed in the first embodiment.

Referring back to FIG. 22, the time signal waveform transmitted in theMBSFN region can be reproduced through the mapping of the symbols of thesignals (that is, the MBSFN-RSs and the signals of the PMCHs)transmitted in the MBSFN region, the IFFT, and the CP insertion. Thereproduced time signal waveform is input as the pilot signal to thecorrelator through the delay adjustment. The received time signalwaveform is also input to the correlator through the RF unit and the A/Dconverter or the like. Then, the delay spread between the signals of theMBSFN region (that is, the identical signals) transmitted in the MBSFNarea 30 is measured through the correlator and an integrator.

The delay between the signals in the symbols included in the MBSFNregion may be measured or the delay between the signals in a part of thesymbols included in the MBSFN region may be measured.

Even in the second embodiment, only the MBSFN-RSs in at least one symbolof the MBSFN region of the specific MBSFN subframes may be transmittedas in the first embodiment. Then, the delay between the MBSFN-RSstransmitted in at least the one symbol may be measured.

The delay measurement result is not limited to the delay spread, but maybe other information. For example, the delay measurement result may beother information indicating delay between the identical signals. Thedelay measurement result may be information indicating the length of theCP allowing the measured delay.

(First Information Acquisition Unit 283)

The first information acquisition unit 283 acquires the result of themeasurement of the delay (that is, the delay measurement result) betweenthe identical signals transmitted in the MBSFN area 30. In the secondembodiment, the first information acquisition unit 283 acquires theresult of the measurement (that is, the delay measurement result) by thesmall base station 200-2 (the measurement unit 281).

(Transmission Control Unit 289)

Transmission of Specification Information

The transmission control unit 289 controls the transmission of thespecification information (that is, the information for specifying thelength of the CP for the MBSFN subframes of the MBSFN area 30) in thesmall cell 20. This point is no different between the first and secondembodiments. Thus, the repeated description will be omitted here.

Transmission of Signal in MBSFN Region

In the second embodiment, only the MBSFN-RSs in at least one symbol ofthe MBSFN region of the specific MBSFN subframes may not be transmitted.Of course, the transmission control unit 289 may control thetransmission such that only the MBSFN-RSs may be transmitted in at leastthe one symbol.

As described above, the small base station 200-2 (the measurement unit281) measures the delay between the identical signals transmitted in theMBSFN area 30. In this case, the transmission control unit 289 may stoptransmitting signals while the measurement target identical signals aretransmitted. For example, the transmission control unit 289 may stoptransmitting the identical signals by the small base station 200-2.

<4.4. Flow of Process>

Next, an example of a process according to the second embodiment will bedescribed with reference to FIG. 25. FIG. 25 is a sequence diagramillustrating an example of a schematic flow of the process according tothe second embodiment.

The control apparatus 100-2 requests the small base station 200-2 of thesmall cell 20 belonging to the MBSFN area 30 to supply the result of themeasurement of the delay (that is, the delay measurement result) betweenthe identical signals (for example, the MBSFN-RSs) transmitted in theMBSFN area 30 (S621). Then, the small base station 200-2 measures thedelay between the identical signals (for example, signals transmitted inthe MBSFN region) transmitted in the MBSFN area 30 (S623). Thereafter,the small base station 200-2 supplies the result of the measurement(that is, the delay measurement result) to the control apparatus 100-2(S625). Based on the delay measurement result, the control apparatus100-2 decides the length of the CP for the MBSFN subframes of the MBSFNarea 30 (S627).

Thereafter, the control apparatus 100-2 transmits the MBMS session startrequest message and the MBMS scheduling information message to the smallbase station 200-2 (S629 and S631). The MBMS session start requestmessage or the MBMS scheduling information message includes thespecification information for specifying the decided length of the CP.Then, the small base station 200-2 reports the system information block(for example, the SIB 13) including the specification information(S633).

The second embodiment has been described above. According to the secondembodiment, the control apparatus 100-2 acquires the result of themeasurement of the delay between the identical signals transmitted inthe MBSFN area 30. Then, based on the result of the measurement, thecontrol apparatus 100-2 decides the length of the CP for the MBSFNsubframes of the MBSFN area 30. Accordingly, for example, it is possibleto use the CP with the more appropriate length in the MBSFN subframes.According to the second embodiment, the delay is measured by the smallbase station 200-2. Accordingly, for example, the delay measurementresult can be obtained without imposing a burden on the terminalapparatus 400-2.

5. APPLICATION EXAMPLES

The technology of the present disclosure is applicable to variousproducts. For example, a control apparatus 100 may be realized as anytype of server such as a tower server, a rack server, and a bladeserver. At least a part of constituent elements of the control apparatus100 may be realized as a module (such as an integrated circuit moduleincluding a single die, and a card or a blade that is inserted into aslot of a blade server) mounted on a server.

For example, the small base station 200 may be realized as an evolvednode B (eNB). In particular, the small base station 200 may be a smalleNB that covers a smaller cell than a macro cell. As one example, thesmall base station 200 may be a home (femto) eNB. As another example,the small base station 200 and the small base station 300 may be a picoeNB or a micro eNB. Instead, the small base station 200 may be realizedas any other types of base stations such as a NodeB and a basetransceiver station (BTS). The small base station 200 may include a mainbody (that is also referred to as a base station apparatus) configuredto control radio communication, and one or more remote radio heads (RRH)disposed in a different place from the main body. Additionally, varioustypes of terminals to be discussed later may also operate as the smallbase station 200 by temporarily or semi-permanently executing a basestation function.

For example, a terminal apparatus 400 may be realized as a mobileterminal such as a smartphone, a tablet personal computer (PC), anotebook PC, a portable game terminal, a portable/dongle type mobilerouter, and a digital camera, or an in-vehicle terminal such as a carnavigation apparatus. At least a part of constituent elements of theterminal apparatus 400 may also be realized as a terminal (that is alsoreferred to as a machine type communication (MTC) terminal) thatperforms machine-to-machine (M2M) communication. Furthermore, theterminal apparatus 400 may be a radio module (such as an integratedcircuit module including a single die) mounted on each of the terminals.

<5.1. Application Example Regarding Control Apparatus>

FIG. 26 is a block diagram illustrating an example of a schematicconfiguration of a server 700 to which the technology of the presentdisclosure may be applied. The server 700 includes a processor 701, amemory 702, a storage 703, a network interface 704, and a bus 706.

The processor 701 may be, for example, a central processing unit (CPU)or a digital signal processor (DSP), and controls functions of theserver 700. The memory 702 includes random access memory (RAM) and readonly memory (ROM), and stores a program that is executed by theprocessor 701 and data. The storage 703 may include a storage mediumsuch as a semiconductor memory and a hard disk.

The network interface 704 is a wired communication interface forconnecting the server 700 to a wired communication network 705. Thewired communication network 705 may be a core network such as an EvolvedPacket Core (EPC), or a packet data network (PDN) such as the Internet.

The bus 706 connects the processor 701, the memory 702, the storage 703,and the network interface 704 to each other. The bus 706 may include twoor more buses (such as a high speed bus and a low speed bus) each ofwhich has different speed.

In the server 700 illustrated in FIG. 26, at least a part of constituentelements (i.e. the request unit 151, the information acquisition unit153, the decision unit 155, and the control unit 157) included in theprocessing unit 130 described with reference to FIG. 17 may beimplemented in the processor 701. As one example, a program causing theprocessor to function as at least the part of constituent elements (inother words, a program causing the processor to perform the operationsof at least the part of constituent elements) may be installed in theserver 700 so that the processor 701 can execute the program. As anotherexample, in the server 700, a module including the processor 701 and thememory 702 may be mounted and at least the part of constituent elementsmay be implemented in the module. In this case, the module may store aprogram causing the processor to function as at least the part ofconstituent elements in the memory 702 and the processor 701 may executethe program. As described above, the server 700 or the module may beprovided as an apparatus including at least the part of constituentelements or the program causing the processor to function as at leastthe part of constituent elements may be provided. A readable storagemedium storing the program may be provided.

<5.2. Application Examples Regarding Base Station> First ApplicationExample

FIG. 27 is a block diagram illustrating a first example of a schematicconfiguration of an eNB to which the technology of the presentdisclosure may be applied. An eNB 800 includes one or more antennas 810and a base station apparatus 820. Each antenna 810 and the base stationapparatus 820 may be connected to each other via an RF cable.

Each of the antennas 810 includes a single or multiple antenna elements(such as multiple antenna elements included in an MIMO antenna), and isused for the base station apparatus 820 to transmit and receive radiosignals. The eNB 800 may include the multiple antennas 810, asillustrated in FIG. 27. For example, the multiple antennas 810 may becompatible with multiple frequency bands used by the eNB 800. AlthoughFIG. 27 illustrates the example in which the eNB 800 includes themultiple antennas 810, the eNB 800 may also include a single antenna810.

The base station apparatus 820 includes a controller 821, a memory 822,a network interface 823, and a radio communication interface 825.

The controller 821 may be, for example, a CPU or a DSP, and operatesvarious functions of a higher layer of the base station apparatus 820.For example, the controller 821 generates a data packet from data insignals processed by the radio communication interface 825, andtransfers the generated packet via the network interface 823. Thecontroller 821 may bundle data from multiple base band processors togenerate the bundled packet, and transfer the generated bundled packet.The controller 821 may have logical functions of performing control suchas radio resource control, radio bearer control, mobility management,admission control, and scheduling. The control may be performed incorporation with an eNB or a core network node in the vicinity. Thememory 822 includes RAM and ROM, and stores a program that is executedby the controller 821, and various types of control data (such as aterminal list, transmission power data, and scheduling data).

The network interface 823 is a communication interface for connectingthe base station apparatus 820 to a core network 824. The controller 821may communicate with a core network node or another eNB via the networkinterface 823. In that case, the eNB 800, and the core network node orthe other eNB may be connected to each other through a logical interface(such as an S1 interface and an X2 interface). The network interface 823may also be a wired communication interface or a radio communicationinterface for radio backhaul. If the network interface 823 is a radiocommunication interface, the network interface 823 may use a higherfrequency band for radio communication than a frequency band used by theradio communication interface 825.

The radio communication interface 825 supports any cellularcommunication scheme such as Long Term Evolution (LTE) and LTE-Advanced,and provides radio connection to a terminal positioned in a cell of theeNB 800 via the antenna 810. The radio communication interface 825 maytypically include, for example, a baseband (BB) processor 826 and an RFcircuit 827. The BB processor 826 may perform, for example,encoding/decoding, modulating/demodulating, andmultiplexing/demultiplexing, and performs various types of signalprocessing of layers (such as L1, medium access control (MAC), radiolink control (RLC), and a packet data convergence protocol (PDCP)). TheBB processor 826 may have a part or all of the above-described logicalfunctions instead of the controller 821. The BB processor 826 may be amemory that stores a communication control program, or a module thatincludes a processor and a related circuit configured to execute theprogram. Updating the program may allow the functions of the BBprocessor 826 to be changed. The module may be a card or a blade that isinserted into a slot of the base station apparatus 820. Alternatively,the module may also be a chip that is mounted on the card or the blade.Meanwhile, the RF circuit 827 may include, for example, a mixer, afilter, and an amplifier, and transmits and receives radio signals viathe antenna 810.

The radio communication interface 825 may include the multiple BBprocessors 826, as illustrated in FIG. 27. For example, the multiple BBprocessors 826 may be compatible with multiple frequency bands used bythe eNB 800. The radio communication interface 825 may include themultiple RF circuits 827, as illustrated in FIG. 27. For example, themultiple RF circuits 827 may be compatible with multiple antennaelements. Although FIG. 27 illustrates the example in which the radiocommunication interface 825 includes the multiple BB processors 826 andthe multiple RF circuits 827, the radio communication interface 825 mayalso include a single BB processor 826 or a single RF circuit 827.

In the eNB 800 illustrated in FIG. 27, at least a part of constituentelements (i.e. the request unit 271, the first information acquisitionunit 273, the information supply unit 275, the second informationacquisition unit 277, and the transmission control unit 279) included inthe processing unit 350 described with reference to FIG. 20 may beimplemented in the radio communication interface 825. Alternatively, atleast the part of constituent elements may be implemented in thecontroller 821. As one example, in the eNB 800, a part (for example, theBB processor 826) or all of the radio communication interface 825 and/ora module including the controller 821 may be mounted, and at least thepart of constituent elements may be implemented in the module. In thiscase, the module may store a program causing the processor to functionas at least the part of constituent elements (in other words, a programcausing the processor to perform the operations of at least the part ofconstituent elements) and may execute the program. As another example, aprogram causing the processor to function as at least the part ofconstituent elements may be installed in the eNB 800, and the radiocommunication interface 825 (for example, the BB processor 826) and/orthe controller 821 may execute the program. As described above, the eNB800, the base station apparatus 820, or the module may be provided as anapparatus including at least the part of constituent elements, or aprogram causing the processor to function as at least the part ofconstituent elements may be provided. A readable storage medium storingthe program may be provided. In regard to this point, at least a part ofthe constituent elements included in the processing unit 280 describedwith reference to FIG. 24 is also the same as at least a part of theconstituent elements included in the processing unit 270.

Second Application Example

FIG. 28 is a block diagram illustrating a second example of a schematicconfiguration of an eNB to which the technology of the presentdisclosure may be applied. An eNB 830 includes one or more antennas 840,a base station apparatus 850, and an RRH 860. Each antenna 840 and theRRH 860 may be connected to each other via an RF cable. The base stationapparatus 850 and the RRH 860 may be connected to each other via a highspeed line such as an optical fiber cable.

Each of the antennas 840 includes a single or multiple antenna elements(such as multiple antenna elements included in an MIMO antenna), and isused for the RRH 860 to transmit and receive radio signals. The eNB 830may include the multiple antennas 840, as illustrated in FIG. 28. Forexample, the multiple antennas 840 may be compatible with multiplefrequency bands used by the eNB 830. Although FIG. 28 illustrates theexample in which the eNB 830 includes the multiple antennas 840, the eNB830 may also include a single antenna 840.

The base station apparatus 850 includes a controller 851, a memory 852,a network interface 853, a radio communication interface 855, and aconnection interface 857. The controller 851, the memory 852, and thenetwork interface 853 are the same as the controller 821, the memory822, and the network interface 823 described with reference to FIG. 33.

The radio communication interface 855 supports any cellularcommunication scheme such as LTE and LTE-Advanced, and provides radiocommunication to a terminal positioned in a sector corresponding to theRRH 860 via the RRH 860 and the antenna 840. The radio communicationinterface 855 may typically include, for example, a BB processor 856.The BB processor 856 is the same as the BB processor 826 described withreference to FIG. 27, except the BB processor 856 is connected to the RFcircuit 864 of the RRH 860 via the connection interface 857. The radiocommunication interface 855 may include the multiple BB processors 856,as illustrated in FIG. 28. For example, the multiple BB processors 856may be compatible with multiple frequency bands used by the eNB 830.Although FIG. 28 illustrates the example in which the radiocommunication interface 855 includes the multiple BB processors 856, theradio communication interface 855 may also include a single BB processor856.

The connection interface 857 is an interface for connecting the basestation apparatus 850 (radio communication interface 855) to the RRH860. The connection interface 857 may also be a communication module forcommunication in the above-described high speed line that connects thebase station apparatus 850 (radio communication interface 855) to theRRH 860.

The RRH 860 includes a connection interface 861 and a radiocommunication interface 863.

The connection interface 861 is an interface for connecting the RRH 860(radio communication interface 863) to the base station apparatus 850.The connection interface 861 may also be a communication module forcommunication in the above-described high speed line.

The radio communication interface 863 transmits and receives radiosignals via the antenna 840. The radio communication interface 863 maytypically include, for example, the RF circuit 864. The RF circuit 864may include, for example, a mixer, a filter, and an amplifier, andtransmits and receives radio signals via the antenna 840. The radiocommunication interface 863 may include multiple RF circuits 864, asillustrated in FIG. 28. For example, the multiple RF circuits 864 maysupport multiple antenna elements. Although FIG. 28 illustrates theexample in which the radio communication interface 863 includes themultiple RF circuits 864, the radio communication interface 863 may alsoinclude a single RF circuit 864.

In the eNB 830 illustrated in FIG. 28, at least a part of constituentelements (i.e. the request unit 271, the first information acquisitionunit 273, the information supply unit 275, the second informationacquisition unit 277, and the transmission control unit 279) included inthe processing unit 270 described with reference to FIG. 20 may beimplemented in the radio communication interface 855 and/or the radiocommunication interface 863. Alternatively, at least the part ofconstituent elements may be implemented in the controller 851. As oneexample, in the eNB 830, a module including a part (for example, the BBprocessor 856) or all of the radio communication interface 855 and/orthe controller 851 may be mounted, and at least the part of constituentelements may be implemented in the module. In this case, the module maystore a program causing the processor to function as at least the partof constituent elements (in other words, a program causing the processorto perform the operations of at least the part of constituent elements)and may execute the program. As another example, a program causing theprocessor to function as at least the part of constituent elements maybe installed in the eNB 830, and the radio communication interface 855(for example, the BB processor 856) and/or the controller 851 mayexecute the program. As described above, the eNB 830, the base stationapparatus 850, or the module may be provided as an apparatus includingat least the part of constituent elements, or a program causing theprocessor to function as at least the part of constituent elements maybe provided. A readable storage medium storing the program may beprovided. In regard to this point, at least a part of the constituentelements included in the processing unit 280 described with reference toFIG. 24 is also the same as at least a part of the constituent elementsincluded in the processing unit 270.

<5.3. Application Examples Regarding Terminal Apparatus> FirstApplication Example

FIG. 29 is a block diagram illustrating an example of a schematicconfiguration of a smartphone 900 to which the technology of the presentdisclosure may be applied. The smartphone 900 includes a processor 901,a memory 902, a storage 903, an external connection interface 904, acamera 906, a sensor 907, a microphone 908, an input device 909, adisplay device 910, a speaker 911, a radio communication interface 912,one or more antenna switches 915, one or more antennas 916, a bus 917, abattery 918, and an auxiliary controller 919.

The processor 901 may be, for example, a CPU or a system on a chip(SoC), and controls functions of an application layer and another layerof the smartphone 900. The memory 902 includes RAM and ROM, and stores aprogram that is executed by the processor 901, and data. The storage 903may include a storage medium such as a semiconductor memory and a harddisk. The external connection interface 904 is an interface forconnecting an external device such as a memory card and a universalserial bus (USB) device to the smartphone 900.

The camera 906 includes an image sensor such as a charge coupled device(CCD) and a complementary metal oxide semiconductor (CMOS), andgenerates a captured image. The sensor 907 may include a group ofsensors such as a measurement sensor, a gyro sensor, a geomagneticsensor, and an acceleration sensor. The microphone 908 converts soundsthat are input to the smartphone 900 to audio signals. The input device909 includes, for example, a touch sensor configured to detect touchonto a screen of the display device 910, a keypad, a keyboard, a button,or a switch, and receives an operation or an information input from auser. The display device 910 includes a screen such as a liquid crystaldisplay (LCD) and an organic light-emitting diode (OLED) display, anddisplays an output image of the smartphone 900. The speaker 911 convertsaudio signals that are output from the smartphone 900 to sounds.

The radio communication interface 912 supports any cellularcommunication scheme such as LTE and LTE-Advanced, and performs radiocommunication. The radio communication interface 912 may typicallyinclude, for example, a BB processor 913 and an RF circuit 914. The BBprocessor 913 may perform, for example, encoding/decoding,modulating/demodulating, and multiplexing/demultiplexing, and performsvarious types of signal processing for radio communication. Meanwhile,the RF circuit 914 may include, for example, a mixer, a filter, and anamplifier, and transmits and receives radio signals via the antenna 916.The radio communication interface 912 may also be a one chip module thathas the BB processor 913 and the RF circuit 914 integrated thereon. Theradio communication interface 912 may include the multiple BB processors913 and the multiple RF circuits 914, as illustrated in FIG. 29.Although FIG. 29 illustrates the example in which the radiocommunication interface 912 includes the multiple BB processors 913 andthe multiple RF circuits 914, the radio communication interface 912 mayalso include a single BB processor 913 or a single RF circuit 914.

Furthermore, in addition to a cellular communication scheme, the radiocommunication interface 912 may support another type of radiocommunication scheme such as a short-distance wireless communicationscheme, a near field communication scheme, and a radio local areanetwork (LAN) scheme. In that case, the radio communication interface912 may include the BB processor 913 and the RF circuit 914 for eachradio communication scheme.

Each of the antenna switches 915 switches connection destinations of theantennas 916 among multiple circuits (such as circuits for differentradio communication schemes) included in the radio communicationinterface 912.

Each of the antennas 916 includes a single or multiple antenna elements(such as multiple antenna elements included in an MIMO antenna), and isused for the radio communication interface 912 to transmit and receiveradio signals. The smartphone 900 may include the multiple antennas 916,as illustrated in FIG. 29. Although FIG. 29 illustrates the example inwhich the smartphone 900 includes the multiple antennas 916, thesmartphone 900 may also include a single antenna 916.

Furthermore, the smartphone 900 may include the antenna 916 for eachradio communication scheme. In that case, the antenna switches 915 maybe omitted from the configuration of the smartphone 900.

The bus 917 connects the processor 901, the memory 902, the storage 903,the external connection interface 904, the camera 906, the sensor 907,the microphone 908, the input device 909, the display device 910, thespeaker 911, the radio communication interface 912, and the auxiliarycontroller 919 to each other. The battery 918 supplies power to blocksof the smartphone 900 illustrated in FIG. 29 via feeder lines, which arepartially shown as dashed lines in the figure. The auxiliary controller919 operates a minimum necessary function of the smartphone 900, forexample, in a sleep mode.

In the smartphone 900 illustrated in FIG. 29, at least one of themeasurement unit 461 and the information supply unit 463 described withreference to FIG. 21 may be implemented in the radio communicationinterface 912. Alternatively, at least one of the measurement unit 461and the information supply unit 463 may be implemented in the processor901 in the auxiliary controller 919. As one example, in the smartphone900, a module including a part (for example, the BB processor 913) orall of the radio communication interface 912, the processor 901, and/orthe auxiliary controller 919 may be mounted, and at least one of themeasurement unit 461 and the information supply unit 463 may beimplemented in the module. In this case, the module may store a programcausing the processor to function as at least one of the measurementunit 461 and the information supply unit 463 (in other words, a programcausing the processor to perform the operations of at least one of themeasurement unit 461 and the information supply unit 463) and mayexecute the program. As another example, a program causing the processorto function as at least one of the measurement unit 461 and theinformation supply unit 463 may be installed in the smartphone 900, andthe radio communication interface 912 (for example, the BB processor913), the processor 901, and/or the auxiliary controller 919 may executethe program. As described above, the smartphone 900 or the module may beprovided as an apparatus including at least one of the measurement unit461 and the information supply unit 463, or a program causing theprocessor to function as at least one of the measurement unit 461 andthe information supply unit 463 may be provided. A readable storagemedium storing the program may be provided.

Second Application Example

FIG. 30 is a block diagram illustrating an example of a schematicconfiguration of a car navigation apparatus 920 to which the technologyof the present disclosure may be applied. The car navigation apparatus920 includes a processor 921, a memory 922, a global positioning system(GPS) module 924, a sensor 925, a data interface 926, a content player927, a storage medium interface 928, an input device 929, a displaydevice 930, a speaker 931, a radio communication interface 933, one ormore antenna switches 936, one or more antennas 937, and a battery 938.

The processor 921 may be, for example, a CPU or a SoC, and controls anavigation function and another function of the car navigation apparatus920. The memory 922 includes RAM and ROM, and stores a program that isexecuted by the processor 921, and data.

The GPS module 924 uses GPS signals received from a GPS satellite tomeasure a position (such as latitude, longitude, and altitude) of thecar navigation apparatus 920. The sensor 925 may include a group ofsensors such as a gyro sensor, a geomagnetic sensor, and an air pressuresensor. The data interface 926 is connected to, for example, anin-vehicle network 941 via a terminal that is not shown, and acquiresdata generated by the vehicle, such as vehicle speed data.

The content player 927 reproduces content stored in a storage medium(such as a CD and a DVD) that is inserted into the storage mediuminterface 928. The input device 929 includes, for example, a touchsensor configured to detect touch onto a screen of the display device930, a button, or a switch, and receives an operation or an informationinput from a user. The display device 930 includes a screen such as aLCD or an OLED display, and displays an image of the navigation functionor content that is reproduced. The speaker 931 outputs sounds of thenavigation function or the content that is reproduced.

The radio communication interface 933 supports any cellularcommunication scheme such as LTE and LTE-Advanced, and performs radiocommunication. The radio communication interface 933 may typicallyinclude, for example, a BB processor 934 and an RF circuit 935. The BBprocessor 934 may perform, for example, encoding/decoding,modulating/demodulating, and multiplexing/demultiplexing, and performsvarious types of signal processing for radio communication. Meanwhile,the RF circuit 935 may include, for example, a mixer, a filter, and anamplifier, and transmits and receives radio signals via the antenna 937.The radio communication interface 933 may be a one chip module havingthe BB processor 934 and the RF circuit 935 integrated thereon. Theradio communication interface 933 may include the multiple BB processors934 and the multiple RF circuits 935, as illustrated in FIG. 30.Although FIG. 30 illustrates the example in which the radiocommunication interface 933 includes the multiple BB processors 934 andthe multiple RF circuits 935, the radio communication interface 933 mayalso include a single BB processor 934 or a single RF circuit 935.

Furthermore, in addition to a cellular communication scheme, the radiocommunication interface 933 may support another type of radiocommunication scheme such as a short-distance wireless communicationscheme, a near field communication scheme, and a radio LAN scheme. Inthat case, the radio communication interface 933 may include the BBprocessor 934 and the RF circuit 935 for each radio communicationscheme.

Each of the antenna switches 936 switches connection destinations of theantennas 937 among multiple circuits (such as circuits for differentradio communication schemes) included in the radio communicationinterface 933.

Each of the antennas 937 includes a single or multiple antenna elements(such as multiple antenna elements included in an MIMO antenna), and isused for the radio communication interface 933 to transmit and receiveradio signals. The car navigation apparatus 920 may include the multipleantennas 937, as illustrated in FIG. 30. Although FIG. 30 illustratesthe example in which the car navigation apparatus 920 includes themultiple antennas 937, the car navigation apparatus 920 may also includea single antenna 937.

Furthermore, a FIG. 30 car navigation apparatus 920 may include theantenna 937 for each radio communication scheme. In that case, theantenna switches 936 may be omitted from the configuration of the carnavigation apparatus 920.

The battery 938 supplies power to blocks of the car navigation apparatus920 illustrated in FIG. 36 via feeder lines that are partially shown asdashed lines in the figure. The battery 938 accumulates power suppliedform the vehicle.

In the car navigation apparatus 920 illustrated in FIG. 30, at least oneof the measurement unit 461 and the information supply unit 463described with reference to FIG. 21 may be implemented in the radiocommunication interface 933. Alternatively, at least one of themeasurement unit 461 and the information supply unit 463 may beimplemented in the processor 921. As one example, in the car navigationapparatus 920, a module including a part (for example, the BB processor934) or all of the radio communication interface 933 and/or theprocessor 921 may be mounted, and at least one of the measurement unit461 and the information supply unit 463 may be implemented in themodule. In this case, the module may store a program causing theprocessor to function as at least one of the measurement unit 461 andthe information supply unit 463 (in other words, a program causing theprocessor to perform the operations of at least one of the measurementunit 461 and the information supply unit 463) and may execute theprogram. As another example, a program causing the processor to functionas at least one of the measurement unit 461 and the information supplyunit 463 may be installed in the car navigation apparatus 920, and theradio communication interface 933 (for example, the BB processor 934)and/or the processor 921 may execute the program. As described above,the car navigation apparatus 920 or the module may be provided as anapparatus including at least one of the measurement unit 461 and theinformation supply unit 463, or a program causing the processor tofunction as at least one of the measurement unit 461 and the informationsupply unit 463 may be provided. A readable storage medium storing theprogram may be provided.

The technology of the present disclosure may also be realized as anin-vehicle system (or a vehicle) 940 including one or more blocks of thecar navigation apparatus 920, the in-vehicle network 941, and a vehiclemodule 942. That is, the in-vehicle system (or a vehicle) 940 may beprovided as an apparatus including at least one of the measurement unit461 and the information supply unit 463. The vehicle module 942generates vehicle data such as vehicle speed, engine speed, and troubleinformation, and outputs the generated data to the in-vehicle network941.

6. CONCLUSION

Each apparatus and each process according to the embodiments of thepresent disclosure have been described above with reference to FIGS. 1to 30.

According to the embodiments of the present disclosure, the controlapparatus 100 acquires the result of the measurement of the delaybetween the identical signals transmitted in the MBSFN area 30 anddecides the length of the CP for the MBSFN subframes of the MBSFN area30 based on the result of the measurement.

According to the embodiments of the present disclosure, the small basestation 200 acquires the result of the measurement of the delay betweenthe identical signals transmitted in the MBSFN area and supplies theresult of the measurement to the control apparatus 100 that decides thecyclic prefix length for the MBSFN subframes of the MBSFN area.

According to the embodiments of the present disclosure, the small basestation 200 or the terminal apparatus 400 measures the delay between theidentical signals transmitted in the MBSFN area.

Accordingly, for example, it is possible to use the CP with the moreappropriate length in the MBSFN subframes.

According to the first embodiment of the present disclosure, the smallbase station 200 controls the transmission such that only the MBSFNreference signals are transmitted in at least one symbol in the MBSFNregion of the specific MBSFN subframes.

Accordingly, for example, the time signal waveform in at least onesymbol of the MBSFN region becomes a known waveform in the terminalapparatus 400. Therefore, the terminal apparatus 400 can know thereception timings of the MBSFN-RSs transmitted by the small basestations 200 of the plurality of small cells 20 belonging to the MBSFNarea 30. Thus, the terminal apparatus 400 can measure the delay betweenthe MBSFN-RSs (that is, the identical signals) transmitted in the MBSFNarea 30.

According to the first embodiment of the present disclosure, the smallbase station 200 acquires the specification information for specifyingthe cyclic prefix length for the MBSFN subframes of the MBSFN area andcontrols the transmission of the specification information in the cell.

Accordingly, for example, the decided length of the CP can actually beused in the terminal apparatus 400. There may be no burden on thedetermination of the length of the CP by the terminal apparatus 400.

The preferred embodiment(s) of the present disclosure has/have beendescribed above with reference to the accompanying drawings, whilst thepresent disclosure is not limited to the above examples. A personskilled in the art may find various alterations and modifications withinthe scope of the appended claims, and it should be understood that theywill naturally come under the technical scope of the present disclosure.

For example, the embodiments in which attention is paid to the smallbase station have been described, but an embodiment of the presentdisclosure is not limited to the related example. For example, theoperation of the above-described small base station may be performed bythe macro base station. That is, the technology according to the presentdisclosure can be applied not only to the small base station but also tothe macro base station.

For example, the example in which the communication system is a systemthat conforms to LTE, LTE-Advanced, or a communication standardequivalent thereto has been described, but an embodiment of the presentdisclosure is not limited thereto. For example, the communication systemmay be a system that conforms to another communication standard.

The processing steps in the processes of the present specification maynot necessarily be performed chronologically in the orders described inthe flowcharts or the sequence diagrams. For example, the processingsteps in the processes may be performed in different orders from theorders described in the flowcharts or the sequence diagrams or may beperformed in parallel.

It is also possible to generate a computer program causing theprocessors (for example, CPUs or DSPs) included in the nodes (forexample, the control apparatus, the small base station, and/or theterminal apparatus) of the present specification to function as theconstituent elements (for example, the information acquisition unit andthe decision unit) of the nodes (in other words, a computer programcausing the processor to perform the operations of the constituentelements of the nodes). A storage medium storing the computer programmay be provided. An apparatus (for example, an apparatus body or amodule (a processing circuit, a chip, or the like) for the apparatusbody) including a memory storing the computer program and one or moreprocessors capable of executing the computer program may also beprovided.

In addition, the effects described in the present specification aremerely illustrative and demonstrative, and not limitative. In otherwords, the technology according to the present disclosure can exhibitother effects that are evident to those skilled in the art along with orinstead of the effects based on the present specification.

Additionally, the present technology may also be configured as below.

(1) An apparatus including:

an acquisition unit configured to acquire a result of measurement ofdelay between identical signals transmitted in an MBSFN area; and

a decision unit configured to decide a cyclic prefix length for an MBSFNsubframe of the MBSFN area based on the result of the measurement.

(2) The apparatus according to (1),

wherein the decision unit decides a normal cyclic prefix length as thecyclic prefix length.

(3) The apparatus according to (2),

wherein the MBSFN subframe includes 14 symbols when the cyclic prefixlength for the MBSFN subframe is the normal cyclic prefix length.

(4) The apparatus according to any one of (1) to (3),

wherein the result of the measurement is a delay spread between theidentical signals.

(5) The apparatus according to any one of (1) to (4),

wherein the identical signals are MBSFN reference signals.

(6) An apparatus including:

an acquisition unit configured to acquire a result of measurement ofdelay between identical signals transmitted in an MBSFN area; and

a supply unit configured to supply the result of the measurement to acontrol apparatus that decides a cyclic prefix length for an MBSFNsubframe of the MBSFN area.

(7) An apparatus including:

a measurement unit configured to measure delay between identical signalstransmitted in an MBSFN area.

(8) The apparatus according to (7),

wherein the apparatus is a terminal apparatus or a module for theterminal apparatus.

(9) The apparatus according to (7),

wherein the apparatus is a base station, a base station apparatus forthe base station, or a module for the base station apparatus.

(10) An apparatus including:

a control unit configured to control transmission such that only anMBSFN reference signal is transmitted in at least one symbol in an MBSFNregion of a specific MBSFN subframe.

(11) An apparatus including:

an acquisition unit configured to acquire specification information forspecifying a cyclic prefix length for an MBSFN subframe of an MBSFNarea; and

a control unit configured to control transmission of the specificationinformation in a cell.

(12) The apparatus according to (11),

wherein the acquisition unit acquires a system information blockincluding the specification information, and

wherein the control unit controls transmission of the system informationblock.

(13) A method including:

acquiring a result of measurement of delay between identical signalstransmitted in an MBSFN area; and

deciding, by a processor, a cyclic prefix length for an MBSFN subframeof the MBSFN area based on the result of the measurement.

(14) A program for causing a processor to execute:

acquiring a result of measurement of delay between identical signalstransmitted in an MBSFN area; and

deciding a cyclic prefix length for an MBSFN subframe of the MBSFN areabased on the result of the measurement.

(15) A readable recording medium having a program recorded thereon, theprogram causing a processor to execute:

acquiring a result of measurement of delay between identical signalstransmitted in an MBSFN area; and

deciding a cyclic prefix length for an MBSFN subframe of the MBSFN areabased on the result of the measurement.

(16) A method including:

acquiring a result of measurement of delay between identical signalstransmitted in an MBSFN area; and

supplying, by a processor, the result of the measurement to a controlapparatus that decides a cyclic prefix length for an MBSFN subframe ofthe MBSFN area.

(17) A program for causing a processor to execute:

acquiring a result of measurement of delay between identical signalstransmitted in an MBSFN area; and

supplying the result of the measurement to a control apparatus thatdecides a cyclic prefix length for an MBSFN subframe of the MBSFN area.

(18) A readable recording medium having a program recorded thereon, theprogram causing a processor to execute:

acquiring a result of measurement of delay between identical signalstransmitted in an MBSFN area; and

supplying the result of the measurement to a control apparatus thatdecides a cyclic prefix length for an MBSFN subframe of the MBSFN area.

(19) A method including:

measuring, by a processor, delay between identical signals transmittedin an MBSFN area.

(20) A program for causing a processor to execute:

measuring delay between identical signals transmitted in an MBSFN area.

(21) A readable recording medium having a program recorded thereon, theprogram causing a processor to execute:

measuring delay between identical signals transmitted in an MBSFN area.

(22) A method including:

controlling, by a processor, transmission such that only an MBSFNreference signal is transmitted in at least one symbol in an MBSFNregion of a specific MBSFN subframe.

(23) A program for causing a processor to execute:

controlling transmission such that only an MBSFN reference signal istransmitted in at least one symbol in an MBSFN region of a specificMBSFN subframe.

(24) A readable recording medium having a program recorded thereon, theprogram causing a processor to execute:

controlling transmission such that only an MBSFN reference signal istransmitted in at least one symbol in an MBSFN region of a specificMBSFN subframe.

(25) A method including:

acquiring specification information for specifying a cyclic prefixlength for an MBSFN subframe of an MBSFN area; and

controlling, by a processor, transmission of the specificationinformation in a cell.

(26) A program for causing a processor to execute:

acquiring specification information for specifying a cyclic prefixlength for an MBSFN subframe of an MBSFN area; and

controlling transmission of the specification information in a cell.

(27) A readable recording medium having a program recorded thereon, theprogram causing a processor to perform:

acquiring specification information for specifying a cyclic prefixlength for an MBSFN subframe of an MBSFN area; and

controlling transmission of the specification information in a cell.

REFERENCE SIGNS LIST

-   1 communication system-   10 macro cell-   11 macro base station-   20 small cell-   100 control apparatus-   151 request unit-   153 information acquisition unit-   155 decision unit-   157 control unit-   200 small base station-   281 measurement unit-   275, 285 information supply unit-   271 request unit-   273, 283 first information acquisition unit-   277, 287 second information acquisition unit-   279, 289 transmission control unit-   400 terminal apparatus-   461 measurement unit-   463 information supply unit

1. An apparatus comprising: an acquisition unit configured to acquire aresult of measurement of delay between identical signals transmitted inan MBSFN area; and a decision unit configured to decide a cyclic prefixlength for an MBSFN subframe of the MBSFN area based on the result ofthe measurement.
 2. The apparatus according to claim 1, wherein thedecision unit decides a normal cyclic prefix length as the cyclic prefixlength.
 3. The apparatus according to claim 2, wherein the MBSFNsubframe includes 14 symbols when the cyclic prefix length for the MBSFNsubframe is the normal cyclic prefix length.
 4. The apparatus accordingto claim 1, wherein the result of the measurement is a delay spreadbetween the identical signals.
 5. The apparatus according to claim 1,wherein the identical signals are MBSFN reference signals.
 6. Anapparatus comprising: an acquisition unit configured to acquire a resultof measurement of delay between identical signals transmitted in anMBSFN area; and a supply unit configured to supply the result of themeasurement to a control apparatus that decides a cyclic prefix lengthfor an MBSFN subframe of the MBSFN area.
 7. An apparatus comprising: ameasurement unit configured to measure delay between identical signalstransmitted in an MBSFN area.
 8. The apparatus according to claim 7,wherein the apparatus is a terminal apparatus or a module for theterminal apparatus.
 9. The apparatus according to claim 7, wherein theapparatus is a base station, a base station apparatus for the basestation, or a module for the base station apparatus.
 10. An apparatuscomprising: a control unit configured to control transmission such thatonly an MBSFN reference signal is transmitted in at least one symbol inan MBSFN region of a specific MBSFN subframe.
 11. An apparatuscomprising: an acquisition unit configured to acquire specificationinformation for specifying a cyclic prefix length for an MBSFN subframeof an MBSFN area; and a control unit configured to control transmissionof the specification information in a cell.
 12. The apparatus accordingto claim 11, wherein the acquisition unit acquires a system informationblock including the specification information, and wherein the controlunit controls transmission of the system information block.